package servlets;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MyServlet extends HttpServlet {

    private List<String> messages = new ArrayList<String>();

    //Returns 0 if the user's input is malicious
    public int validate(String txtField)
    {
        StringBuilder sb = new StringBuilder();
        sb.append(txtField);
        for(int i = 0; i < sb.length(); i++)
        {
            if(sb.charAt(i) == '\'' || sb.charAt(i) == '"' || sb.charAt(i) == ',' || sb.charAt(i) == ';'  ||
               sb.charAt(i) == '*'  || sb.charAt(i) == '%' || sb.charAt(i) == '_' || sb.charAt(i) == '&'  ||
               sb.charAt(i) == '\\' || sb.charAt(i) == '|' || sb.charAt(i) == '?' || sb.charAt(i) == '~'  ||
               sb.charAt(i) == '<'  || sb.charAt(i) == '>' || sb.charAt(i) == '^' || sb.charAt(i) == '('  ||
               sb.charAt(i) == ')' || sb.charAt(i) == '[' || sb.charAt(i) == ']'  || sb.charAt(i) == '{'  ||
               sb.charAt(i) == '}' || sb.charAt(i) == '$' || sb.charAt(i) == '\n' || sb.charAt(i) == '\r')
            {
                return 0;
            }
        }
        return 1;
    }


    /**
     * Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");

        String message = (String)request.getParameter("txtComments");

        int check = validate(message);
        if(check == 1)
        {
            messages.add(0, message);
            request.getSession().setAttribute("messages", messages);
            response.sendRedirect(request.getContextPath() + "/index.jsp");
        }
        else
        {
            PrintWriter out = response.getWriter();
            try
            {
                response.sendRedirect(request.getContextPath() + "/error.jsp");
                //TODO output your page here
                out.println("<html>");
                out.println("<head>");
                out.println("<title>Servlet MyServlet</title>");
                out.println("</head>");
                out.println("<body>");
                out.println("<h1>Your input should not contain</h1>");
                out.println("</body>");
                out.println("</html>");
            }
            finally
            {
                out.close();
            }
        }
    }

    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /**
     * Handles the HTTP <code>GET</code> method.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Handles the HTTP <code>POST</code> method.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Returns a short description of the servlet.
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>

}
